зеркало из https://github.com/mozilla/gecko-dev.git
58 строки
1.8 KiB
C
58 строки
1.8 KiB
C
/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef GFX_COLOR_H
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#define GFX_COLOR_H
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#include "mozilla/Attributes.h" // for MOZ_ALWAYS_INLINE
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#include "mozilla/EndianUtils.h" // for mozilla::NativeEndian::swapToBigEndian
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/**
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* Fast approximate division by 255. It has the property that
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* for all 0 <= n <= 255*255, GFX_DIVIDE_BY_255(n) == n/255.
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* But it only uses two adds and two shifts instead of an
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* integer division (which is expensive on many processors).
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*
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* equivalent to ((v)/255)
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*/
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#define GFX_DIVIDE_BY_255(v) \
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(((((unsigned)(v)) << 8) + ((unsigned)(v)) + 255) >> 16)
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/**
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* Fast premultiply
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*
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* equivalent to (((c)*(a))/255)
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*/
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uint8_t MOZ_ALWAYS_INLINE gfxPreMultiply(uint8_t c, uint8_t a) {
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return GFX_DIVIDE_BY_255((c) * (a));
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}
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/**
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* Pack the 4 8-bit channels (A,R,G,B)
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* into a 32-bit packed NON-premultiplied pixel.
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*/
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uint32_t MOZ_ALWAYS_INLINE gfxPackedPixelNoPreMultiply(uint8_t a, uint8_t r,
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uint8_t g, uint8_t b) {
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return (((a) << 24) | ((r) << 16) | ((g) << 8) | (b));
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}
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/**
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* Pack the 4 8-bit channels (A,R,G,B)
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* into a 32-bit packed premultiplied pixel.
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*/
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uint32_t MOZ_ALWAYS_INLINE gfxPackedPixel(uint8_t a, uint8_t r, uint8_t g,
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uint8_t b) {
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if (a == 0x00)
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return 0x00000000;
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else if (a == 0xFF) {
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return gfxPackedPixelNoPreMultiply(a, r, g, b);
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} else {
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return ((a) << 24) | (gfxPreMultiply(r, a) << 16) |
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(gfxPreMultiply(g, a) << 8) | (gfxPreMultiply(b, a));
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}
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}
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#endif /* _GFX_COLOR_H */
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